US4435838A
Expired / Lapsed
US
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Method and apparatus for tomographical imaging
Assignee: International Business Machines Corp
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Filing: 1981-11-16
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Granted: 1984-03-06
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Expires: 2001-11-16
Abstract
Abstract The specification concerns a method and apparatus for tomographically imaging different selected planes of a three-dimensional object by detecting radiation through a coded aperture mask, storing an image of the radiation detected over a period of time, and decoding each selected object plane by a correlation process appropriate to the size of the shadow of the mask cast on the detector by points in the selected object plane. Each object plane to be imaged is selected by adjusting one or both of the object/detector and mask/detector separations D and d respectively so that D/d is a constant for all selected object planes. This provides a fixed shadow size of the mask on the detector for all selected object planes, and thus permits the use of a fixed decoding process. In the preferred embodiment the mask is a mosaicked mask based on m-sequences, and the decoding process is implemented in hardware and uses a Fast Hadamard Transform.
Inventors
- 👤 Alexander R. Gourlay
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 11:39
CPC Classifications
A; A61; A61B; A61B6/00; A61B6/02; A61B6/025; A61B6/42; A61B6/4208; A61B6/4258; G; G01; G01T; G01T1/00; G01T1/29; G01T1/2914; G01T1/2921; G01T1/295; G01T1/2985
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
160 words
A method for tomographically imaging different selected planes of a three-dimensional object by detecting radiation from the object after passage of the radiation through a coded aperture mask, storing an image of the radiation detected over a period of time, and for each selected object plane decoding the stored image by a correlation process appropriate to the size of the shadow of the mask cast on the detector by points in the selected object plane, characterised in that: each object plane to be imaged is selected by adjusting the position of at least one of the object, mask, and detector, in such manner that D/d is a constant where D is the distance from the selected object plane to the detection plane and d is the distance from the selected object plane to the mask, a respective radiation image is detected and stored for each object plane thus selected, and each stored image is decoded using a fixed decoding process.
Claim 2
Independent Claim
160 words
A method for tomographically imaging different selected planes of a three-dimensional object by detecting radiation from the object after passage of the radiation through a coded aperture mask, storing an image of the radiation detected over a period of time, and for each selected object plane decoding the stored image by a correlation process appropriate to the size of the shadow of the mask cast on the detector by points in the selected object plane, characterised in that: each object plane to be imaged is selected by adjusting the position of at least one of the object, mask, and detector, in such manner that D/d is a constant where D is the distance from the selected object plane to the detection plane and d is the distance from the selected object plane to the mask, a respective radiation image is detected and stored for each object plane thus selected, and each stored image is decoded using a fixed decoding process.
Claim 3
Dependent Claim
25 words
A method according to claim 1, wherein the coded aperture mask is based on m-sequences, and the fixed decoding process uses a Fast Hadamard Transform.
Claim 4
Dependent Claim
14 words
A method according to claim 2, wherein the coded aperture mask is twofold mosaicked.
Claim 5
Dependent Claim
27 words
A method according to claim 1, 2, or 3, wherein the object-detector separation is substantially constant and different object planes are selected by adjusting the mask-detector separation.
Claim 6
Dependent Claim
12 words
A method according to claim 4, wherein the radiation is gamma radiation.
Claim 7
Dependent Claim
175 words
In an apparatus for tomographically imaging different selected planes of a three-dimensional object by detecting radiation from said object after the passage of the radiation through a coded aperture mask, wherein an image of the radiation of a selected plane sensed by a detector over a period of time is stored, and the decoding of said selected plane is by a correlation process appropriate to the size of the shadow of said mask cast on said detector by points in said selected plane, the improvement comprises: means for adjusting the position of at least one of said object, said mask, or said detector to select each of said different selected planes of said object to be imaged in such a manner that the ratio D/d is a constant, where D is the distance from said selected plane to the plane of said detector, and d is the distance from said selected plane to the plane of said mask; and means for decoding, using a fixed decoding process, each of said selected planes of said object.
Claim 8
Dependent Claim
175 words
In an apparatus for tomographically imaging different selected planes of a three-dimensional object by detecting radiation from said object after the passage of the radiation through a coded aperture mask, wherein an image of the radiation of a selected plane sensed by a detector over a period of time is stored, and the decoding of said selected plane is by a correlation process appropriate to the size of the shadow of said mask cast on said detector by points in said selected plane, the improvement comprises: means for adjusting the position of at least one of said object, said mask, or said detector to select each of said different selected planes of said object to be imaged in such a manner that the ratio D/d is a constant, where D is the distance from said selected plane to the plane of said detector, and d is the distance from said selected plane to the plane of said mask; and means for decoding, using a fixed decoding process, each of said selected planes of said object.
Claim 9
Dependent Claim
30 words
In an apparatus as set forth in claim 6, wherein said encoded aperture mask is based on m-sequences, and said decoding means includes means for performing a Fast Hadamard Transform.
Claim 10
Dependent Claim
17 words
In an apparatus as set forth in claim 7, wherein said coded aperture mask is twofold mosaicked.
Claim 11
Dependent Claim
46 words
In an apparatus as set forth in claim 6, 7 or 8, wherein D is maintained substantially constant, and each of said different selected planes of said object is selected by adjusting the distance between the plane of said mask and the plane of said separation.
Claim 12
Dependent Claim
15 words
In an apparatus as set forth in claim 9, wherein said radiation is gamma radiation.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1987-03-06 | 1987-09-05 | 1988-03-06 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1991-03-06 | 1991-09-05 | 1992-03-06 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1995-03-06 | 1995-09-05 | 1996-03-06 | $7700.00 | Window Closed / Lapsed |